Nucleic acid test (NAT) methods to test plasma mini-pools are being used to screen blood and plasma donors for HCV RNA because these tests can detect viral RNA even when serological tests are negative. Appropriate standards are needed to evaluate the analytical sensitivity because of diverse NAT methods and varied pool sizes. An HCV panel consisting of 10 members with HCV RNA levels ranging from 0 to 10E5 copies/mL has been formulated from a window-period plasma unit, 5 x 10E7 copies/mL of genotype 1b. The panel member #1, 10E3 copies/mL, has been assigned to contain 250 International Unit (IU) of HCV RNA /mL by an international collaborative study in that 5 national HCV working reagents were calibrated against the WHO's HCV International Standard. Stability studies on our HCV panel are in progress. We continued to investigate the extent of parvovirus B19 contamination in plasma derivatives that include Factor VIII concentrates (AHF), immune globulins (both intravenous and intramuscular preparations, IGIVs and IGIM), and albumin products. B19 DNA was very prevalent in human plasma derived AHF (H) but not in porcine AHF. One of the recombinant AHF products was weakly positive. Of 5 manufacturers'(mfrs')AHF(H)products, one mfr's product subjected to a wet-heat viral-inactivation process and purified by immunoaffinity chromatography had the lowest prevalence and, when present, had very low levels of B19 DNA. We also detected low levels of B19 DNA in some lots of IGIV, IGIM, and albumin products. The effects of various viral inactivation/removal (VI/R) steps and methods of purification to this non-enveloped virus are being evaluated. Recently, we participated in investigating some lots of solvent-detergent treated pooled plasma made by one mfr that were recalled because of B19 transmissions. We confirmed that the two implicated lots had a very high level of B19 DNA, >10E8 PCR units/mL. To investigate the presence of free versus complexed virions in these products, buoyant density profiles of B19 are being investigated. Our study on the detection of TT virus (TTV), a recently identified, non-enveloped virus, in plasma derivatives has been completed. TTV DNA was prevalent in AHF (H). It was not detected in porcine AHF, recombinant AHF, IGIV or albumin products. Only one IGIM lot not subject to any viral inactivation procedure had detectable TTV DNA. The prevalence rate in AHF(H)depended upon methods of VI/R and product purification. No TTV DNA was detected in 2 mfrs' AHF(H)lots subjected to immunoaffinity purification. Our data also showed that while S/D treatment was ineffective, TTV was somewhat susceptible to the 60 deg. C/10 h wet-heating process. We continued to perform the lot release testing for HCV RNA in 2 mfrs' IGIM products not yet subjected to any VI procedure in the manufacture.
